Snap-acting switch



Aug. 21., 1945. c, M. OSTERHELD SNAP-ACTING SWITCH Filed Nov. 27, 1944 2 Sheets-Sheet l INVENTOR.

A T To R N av.

clqrkMosterheld Aug. 21, 1945.

C. M. OSTERHELD SNAP-ACTING SWITCH Filed Nov. 27, 1944 2 Sheets-Sheet 2 INVENTOR. Clark M. Osi'er-held.

ATTORNEY.

Patented Aug. 21', 1945 SNAP-ACTING SWITCH Clark M. Osterheld, Stougliton, Wis., assignor to McGraw Electric Company, Elgin,

poration of Delaware 111., a cor- Appllcation November 27, 1944, Serial No. 565,281 7 Claims. c rzoo-las) My invention relates to switches, and particularly to snap-acting switches.

An object of my invention is to provide means in a snap acting switch that shall increase the cooperating contact pressure between the two contacts just before disengagement thereof.

Another object of my inventionis to provide .a

snap-acting toggle switch that shall embody means for reducing the temperature differential of operation thereof.

Other. objects of my invention will either be further a pair of pivot plates l9 secured to the ends of the respective side portions 2| and 23 of the bimetal bar l5. These pivot plates l9 comprise a return bent member having an arcuate intermediateportion, together with two flat end portions which are secured in'any suitable ordesired manner, as, for instance, by rivets 25,

' against the end portions of the sides 2| and 23 evident from a description of one form of device embodying my invention or will be set forth in the course of such description and particularly in the appended claims.

In the drawings,

Figure 1 is a side, elevational view of the toggle switch in full size, shown when in closed position,

Fig. 2 is a longitudinal, central, sectional view of the toggle switch, shown in double size,

Fig, 3 is a side, elevational view of the toggle switch, showing the bimetals when heated and Just before disengagement of the two contact members,

Fig. 4 is a side, elevational view of the switch, showing the positions of the various parts thereof with the switch in open position,

Fig. 5 is a top plan view of Fig. 1,

Fig. 6 is a sectional view, taken on the line 6-6 of Fig. 2,

Fig. '7 is a horizontal, sectional view, taken on the line of Fig. 2, 1

Fig. 8 is a bottom view of the short bimetal bar and the spring arm which engages the connecting piece, as shown in Fig. 10,

Fig. 9 is an end view of the long bimetal bar, the view being taken on the line 9--9 of Fig. 2, and,

Fig. 10 isan end view of the contact bridging member.

The device embodying my invention comprises 1 a base member I l, which may be made of electricinsulating material and which may be of sub-' stantially rectangular shape. I provide thereon a block 13 of electric-insulating material, having secured thereagainst one end of a first bimetal bar l5 as by means of a plurality of short machine screws H, which :re'effective to secure not only the member l3 against the upper surface of base Ii, but also to secure one end of bimetal bar I5 in proper operative position against theouter surface of block l3. The bimetal bar l5 has an elongated recess therein of the bimetal bar l5. It is shown in Fig. 7 of the drawings that the arcuate portions of the pivot plates I9 have indentations 21 therein for a purpose which will hereinafter appear.

I provide further a second bimetal arm 29, which, as will be seen by reference to Fig. 5 of the drawings, is provided also with a longitudinal, central slot 3i therein adjacent its pivoted end, providing two side portions 33' and 35, each of which has a sharp, pointed end adapted to fit into the indentations, 21 in the members l9 on side portions and 23.

I provide further an over center spring 31 positioned withinthe slots l3 and 3|, one end of which is connected with the central portion of the second bar 29, while the other end thereof is connected with the outer end of a third bimetal bar 39, which partially overlaps the recess l8 in bimetal bar 15 and has its other end secured as by a plurality of rivets 4| to the underside of the bimetal bar l5 inv substantially the position shown in Fig. 5 of the drawings. It is to be noted that the bimetal 'bar 39 is of relatively high thermal responsiveness, which is greater than that of bimetal bar I5. It may also be noted that the high expansion component in both bimetal bars l5 and 39 is on the upper surface of the two elements, so that when subjected to an increase of temperature, the bimetal bars will tend to move in a clockwise direction, as shown in Fig. 3 of the drawings, the bimetal bar 39 flexing a greater distance thandoes the bimetal bar I5.

Loosely mounted on bimetal bar 29 is a bridging member 43 made of electric-insulating material of substantially T-shape having its elongated stem 45 extending througlran opening 39 in said bar 29, being retained by cotter pin 41. Secured in any suitable manner against the lower face of member 43 isa metal contact bridging member 49, and is adapted to engage a pair of spaced contact members and 5|, suitably secured against the upper surface of block I l as by a plurality of short machine screws. I provide further a short spring bar 55, one end of which is secured against the lower surface of bimetal bar 29, while the other endextends to or slightly beyond the free end of bimetal bar 29 and between the bimetal bar and the upper surface of the contact bridging member 43. Spring II is initially bent so that it presses against contact bridging member 43, so as to increase the contact pressure between the contact bri ng member 43 and the fixed contacts 50 and II.

I provides stop 51, of substantially L-shape, which has one end thereof secured as by a plurality of short machine screws ll against the upper surface of block ll, so that, as shown in Fig. 4 of the drawings, the upper end of stem 4| of the contact bridging member 43 will engage a bar 6| secured to stop member I! when the switch is open. I provide further means for varying the temperature at which disengagement of contact bridging member 43 from contacts II and II will occur, in the shape of a screw threaded bolt 03 fixed in member ii, having thereon a washer I which is adapted to be adjusted as to its position longitudinally of rod 63 by a put 1. As is well known, the position of washer II on the screwthreaded stud 63 determines the temperature at which disengagement of the contact bridging member 43 will occur from the fixed contacts 4| and SI.

Fig. 2 of the drawings shows the positions of the various parts of the snap-acting thermal switch comprising particularly the bimetal bars I5, 29, and 39 in combination with the over center spring 31 when the switch is closed. Reference to Fig. 3 of the drawings shows the positions of the various elements of the toggle arm snapacting switch when a certain temperature rise of the parts thereof has occurred, but this temperature rise is insufilcient to cause snap-acting disengagement between the contact bridging mem-.

aasaua from the spirit and scope thereof, and all such modifications coming clearly within the scope of the appended claims shall be considered as covered thereby.

I claim as my invention:

1. A thermostatic snap-acting switch com ing a first bimetal bar having one end thereof fixed and having a central longitudinal slot in its other end portion, a second bar positioned in pivotal end-to-end relation to said first bimetal bar and having a central longitudinal slot in its pivotally suppoi' end portion, a second bimetal bar, of greater thermosensitivity than said first bimetal bar having one end thereof mounted on said first bar intermediate the ends thereof to partially overhang the slot in said first bimetal bar and an over center spring in said aligned slots having its ends connected to'said second bar and said second bimetal bar.

2. A thermostatic snap-acting switch comprising a first bimetal bar having one end thereof fixed, a second bar pivotally operatively engaging said first bimetal bar to form a toggle Joint therewith, a second bimetal bar, of greater thermosensitivity than said first bimetal bar, having one end secured to said first Nmetal bar intermediate the ends thereof and having its other end free to fiex more than said first bimetal bar upon change of temperature and an over center spring having its ends connected to the the other end of said second bimetal bar and to said second'bar intermediate the ends thereof.

3. A thermostatic snap-acting switch comprising a pair of pivotally abutting toggle arms, at

her 49 and contacts 50 and BI. It will be noted,

by reference to Fig. 3 of the drawings, that the bimetal bar 39, which, as has been hereinbefore stated, is .of higher thermal sensitivity or responsivenes than is bimetal bar ll, h s fiexed a greater degree, in a clockwise direction, than has bimetal bar IS. The left hand end of over center spring 31 has therefore been moved beyond the position which it would occupy if the left hand end were connected directly to the bimetal bar ii. This position of the left hand end of spring 81 causes an increase in the pressure between the contact bridging member and the fixed contacts 50 and lil. This increased contact pressure is helped also by the springbar I.

This added movement of the left hand end of the over center spring I1 results also in a decrease in the temperature differential of operation of the switch, comprising the partsshown in the present application.

As is well known, in snap-acting switches of this generaljkind, the pressure between the contact bridging member and the fixed contacts tends to approach zero just before disengagement occurs therebetween, with the attendant result that if the change of temperature is very slow, there may be a tendency for the contacts to fry, with resultant arcing and burning or chal'i'ingv of the contacts, whereby upon reengagement thereof a much greater resistance may be included in the circuit than had theretofore been the case.

The device embodying my invention thus provides a relatively simple means for increasing the pressure between the contacts of such a snapacting termally-actuable switch, and for decreasing the temperature differential of operation of such switches.

Various modifications may be made in the device embodying my invention without departing sensitivity and having its other end least one or said arms being of bimetal, a bimetal bar, of relatively high thermosensitivity secured at one of its ends to a longitudinally intermediate portionofoneofsaidpairofarmsandanover centerspringhayingoneendconnectedtothe other end of said bimetal bar of high thermoconnected to the other of said arms.

45A thermostatic snap-actingswitch comprising a pair of pivotally abutting toggle arms. at leastoneofsaidarmsbeingofbimetal andhaving its outer end fixed, a contact member onthe outerendoftheotheramacooperatingfixed contact member, a bimetal bar, of greater thermosensitivity than said bimetal am, having one and secured on said bimetal arm intermediate theendsthereofand beingadaptedtofiexahead of said bimetal arm upon change, of temperature and an over center spring having one end thereof cmnectedtotheotherendofsaidbimetalbar and having its other end connected to said other toggle arm intermediate the thereof and effective to increase the pressure of said contact member on a cooperating fixed contact member Just prior to disengagement therebetween.

5. A thermostatic snap-acting switch comprising two bimetal bars positioned in pivotally abutting end-to-end relation, elongated, centra i, longitudinal slots in the adiacea ends of the twobars, acontaetmemherontheouterendof prior to snap-acting disengagement therefrom.

6. A thermostatic snap-acting switch comprising two bimetal bars positioned in pivotally abutting end-to-end relation, one end of one bar being fixed, elongated, central, longitudinal slots in the abutting ends of the two bars, a contact member loosely supported on the free end of the other of said bars, a fixed contact adapted to be engaged by and disengaged'irom said contact member, a third bimetal bar of greater thermosensitivity than that of the other two bars having one end secured to saidone bar to overhang .the slot in that bar, the high-expansion component of all of said bars being on the same side of the assembly, an over center spring having its end connected to said third bar and to the other bar and' adapted to be positioned in said slots and a leaf spring having one of its ends secured to the other bar intermediate its ends and having its other end adapted to press the contact members into close operative engagement with each other when in engagement, said third bar being adapted to flex more in the same direction than the bar to which it is secured to cause said contact members to be engaged with an appreciable pressure Just prior to snap-acting disengagementtherebetween.

ing two bimetai bars positioned in pivotally abutting end-to-end relation, one end or one bar being fixed, elongated. central, longitudinal slots in the abutting ends of the two bars, a contact member loosely supported on the free end of the other of said bars. a fixed contact adapted to be bar and adapted to be positioned in said slots and a leaf spring having one of its ends secured to the other bar intermediate its ends and having its other end. adapted to press the contact members into close operative engagement with each other when in engagement, said third bar being adapted to flex more in the same direction than the bar to which it is secured to cause said contact members to be engaged with an appreciable pressure just prior to snap-acting disen- Il gagement therebetween, and to reduce the temperature difl'erential of operation or said switch.

7. A thermostatic snap-acting switch compris- V CLARK M. OSTERHELD. 

